Adaptive optics is a field of optics dedicated to the improvement of optical signals using information about signal distortions introduced by the environment in which the optical signals propagate. An excellent introductory text on the subject is given in “Principles of Adaptive Optics” by R. K. Tyson, Academic Press, San Diego, 1991, the teachings of which are incorporated herein by reference.
Interest in the field of adaptive optics has increased in recent years due to the demand for various adaptive optical elements for use in advanced applications such as atmospheric imaging, optical signal processing, optical data storage, high-power lasers, etc. A representative adaptive optical element is a micro-electro-mechanical system (MEMS) device that may be used, for example, in an optical system designed to compensate for signal distortions introduced in an optical image. An appropriate sensor measures the distortions and generates feedback for the MEMS device. Based on the feedback, mirrors of the MEMS device are deformed such that the distortions are significantly reduced, thus improving receiver performance.
One MEMS device, as might be used in the field of adaptive optics or other related fields, is a deformable mirror. In one instance, a deformable mirror is simulated by an array of very small mirrors, each having a reflective layer, torsional members, support posts, and electrostatic actuators (e.g., electrodes) positioned thereunder, the electrostatic actuators configured to control the torsional members, and thus control the shape of the simulated reflective deformable layer. A typical method for manufacturing such a deformable mirror includes forming the electrostatic actuators, support posts, torsional members and reflective surface using conventional materials processing, and thereafter releasing the movable elements (e.g., the torsional members and reflective surface) using a selective etch. Unfortunately, the conventional process for releasing the torsional members and reflective surface has various drawbacks, especially when used in conjunction with hybrid devices encompassing the drive circuitry.
Accordingly, what is needed in the art is an apparatus and method of manufacture therefore that accommodates the issues related to the aforementioned release step.